Method for chemically removing aluminum-containing materials from a substrate

Abstract

A chemical composition for selectively removing an aluminum-containing material from a substrate comprises an acid having a formula of H x AF 6 , a precursor thereof, and a mixture of said acid and said precursor; wherein A is selected from the group consisting of Si, Ge, Ti, Zr, Al, and Ga; and x is in a range from 1 to 6, inclusive. The chemical composition can comprise at least another acid selected from the group consisting of phosphoric acid, nitric acid, sulfuric acid, hydrochloric acid, hydrofluoric acid, hydrobromic acid, hydriodic acid, acetic acid, perchloric acid, phosphorous acid, phosphinic acid, alkyl sulfonic acids, mixtures thereof, and precursors thereof. The chemical composition can be used to remove aluminum seal strips selectively from the dovetail of a turbine-engine blade.

What is claimed is:  
     
         1 . A chemical composition comprising a first compound selected from the group consisting of an acid having a formula of H x AF 6 , a precursor thereof, and a mixture of said acid and said precursor; wherein A is selected from the group consisting of Si, Ge, Ti, Zr, Al, and Ga; and x is in a range from 1 to 6, inclusive; said chemical composition is capable of reacting selectively with an aluminum-containing material.  
     
     
         2 . The chemical composition according to  claim 1 , wherein said first compound is present at a concentration from about 0.05 M to about 5 M.  
     
     
         3 . The chemical composition according to  claim 1 , wherein said first compound is present at a concentration from about 0.2 M to about 3.5 M.  
     
     
         4 . The chemical composition according to  claim 1 , further comprising at least, a second compound selected from the group consisting of phosphoric acid, nitric acid, sulfuric acid, hydrochloric acid, hydrofluoric acid, hydrobromic acid, hydriodic acid, acetic acid, perchloric acid, phosphorous acid, phosphinic acid, alkyl sulfonic acids, and mixtures thereof.  
     
     
         5 . The chemical composition according to  claim 4 , wherein said at least second compound is phosphoric acid.  
     
     
         6 . The chemical composition according to  claim 5 , wherein said at least second compound is present at a concentration from about 0.1 M to about 20 M.  
     
     
         7 . The chemical composition according to  claim 5 , wherein said at least second compound is present at a concentration from about 0.5 M to about 5 M.  
     
     
         8 . The chemical composition according to  claim 5 , further comprising a third compound that comprises hydrochloric acid.  
     
     
         9 . The chemical composition according to  claim 8 , wherein said third compound is present at a concentration from about 0.1 M to about 20 M.  
     
     
         10 . The chemical composition according to  claim 5 , wherein said third compound is present at a concentration from about 0.5 M to about 2 M.  
     
     
         11 . The chemical composition according to  claim 10 , wherein said chemical composition is an aqueous solution of said first compound, said second compound, and said third compound.  
     
     
         12 . A method for selectively removing an aluminum-containing material from a work piece, wherein said work piece comprises a substrate on which said aluminum-containing material is disposed, said method comprising contacting said work piece with a chemical composition that comprises a first compound selected from the group consisting of an acid having a formula of H x AF 6 , a precursor thereof, and a mixture of said acid and said precursor; wherein A is selected from the group consisting of Si, Ge, Ti, Zr, Al, and Ga; and x is in a range from 1 to 6, inclusive; said chemical composition is capable of reacting selectively with an aluminum-containing material.  
     
     
         13 . The method according to  claim 12 , wherein said chemical composition further comprises a second compound selected from the group consisting of phosphoric acid, nitric acid, sulfuric acid, hydrochloric acid, hydrofluoric acid, hydrobromic acid, hydriodic acid, acetic acid, perchloric acid, phosphorous acid, phosphinic acid, alkyl sulfonic acids, and mixtures thereof.  
     
     
         14 . The method according to  claim 12 , wherein said second compound is phosphoric acid.  
     
     
         15 . The method according to  claim 12 , wherein said chemical composition further comprises a third compound that comprises hydrochloric acid.  
     
     
         16 . The method according to  claim 12 , wherein said first compound is present at a concentration in a range from about 0.05 M to about 5 M.  
     
     
         17 . The method according to  claim 12 , wherein said first compound is present at a concentration in a range from about 0.2 M to about 3.5 M.  
     
     
         18 . The method according to  claim 14 , wherein said second compound is present at a concentration in a range from about 0.1 M to about 20 M.  
     
     
         19 . The method according to  claim 14 , wherein said second compound is present at a concentration in a range from about 0.5 M to about 5 M.  
     
     
         20 . The method according to  claim 15 , wherein said third compound is present at a concentration in a range from about 0.1 M to about 20 M.  
     
     
         21 . The method according to  claim 15 , wherein said third compound is present at a concentration in a range from about 0.5 M to about 2 M.  
     
     
         22 . A method for selectively removing an aluminum-containing material from a work piece, wherein said work piece comprises a substrate on which said aluminum-containing material is disposed, said method comprising contacting said work piece with a chemical composition that comprises an acid having a formula of H 2 SiF 6 , phosphoric acid, and hydrochloric acid; said chemical composition is capable of reacting selectively with an aluminum-containing material; wherein said H 2 SiF 6  is present at a concentration in a range from about 0.05 M to about 5 M, said phosphoric acid is present at a concentration in a range from about 0.1 M to about 20 M, and said hydrochloric acid is present at a concentration in a range from about 0.1 to about 20 M.  
     
     
         23 . The method according to  claim 22 , wherein a motion is imparted to said work piece relative to said chemical composition.  
     
     
         24 . The method according to  claim 22 , wherein a motion is imparted to said chemical composition relative to said work piece.  
     
     
         25 . The method according to  claim 22 , wherein both said chemical composition and said work piece are maintained at a temperature up to about 100° C., and said contacting is carried out for a time from about 10 minutes to about 72 hours.  
     
     
         26 . The method according to  claim 22 , wherein said work piece is a turbine-engine blade, and said aluminum-containing material comprises aluminum seal strips disposed on a dovetail of said turbine-engine blade.  
     
     
         27 . The method according to  claim 26 , wherein said turbine-engine blade comprises a material selected from the group consisting of nickel-, cobalt-, and iron-based alloys.